Web strength and tensile tester and method

ABSTRACT

Method and device for rapidly measuring the tensile strength and stretch energy of web materials, particularly materials such as woven or nonwoven reinforced fabrics and tissue papers. The method is characterized by holding the material while it is subjected to action of a reciprocal probe. The apparatus includes a horizontal table having adjustable sections and clamps to produce a variety of test conditions which in combination with the probe allow rapid approximate duplication of conventional and load cell type tensile testers.

Apr. 3, 1973 Elnite States Patet [191 Beckstrom 73/102 .........73/l02 Ostrowski...........................73/102 X [54] WEB STRENGTH AND TENSILE 2,983,139 5/1961 Galbraith et TESTER AND METHOD 3,498,120 3/1970 MacMillan.........

, 3,319,462 5/1967 [75] Inventor: Daniel H. Beckstrom, Winnebago,

Wis.

Primary Examiner-Jerry W. Myracle Attorney-Daniel J. Hanlon et al.

[73] Assignee: Kimberly-Clark Corporation,

Neenah, Wis.

Sept. 2, 1971 [21] Appl. No.: 177,355

[57] ABSTRACT Method and device for rapidly measuring the tensile strength and stretch energy of web materials, particu- 22 Filed:

larly materials such as woven or nonwoven reinforced [52] U 5 Cl fabrics and tissue papers. The method is characterized [51] Int Cl 2 6 3 by holding the material while it is subjected to action of a reciprocal probe. The apparatus includes a horizontal table having adjustable sections and clamps to produce a variety of test conditions which in combination with the probe allow rapid approximate [58] Field of Search.........................

[56] References Cited UNITED STATES PATENTS duplication of conventional and load cell type tensile testers.

1,413,305 4/1922 Webb.....................................73/102 1,878,193 9/1932 Scott et a1. 8 Claims, 3 Drawing Figures WEB STRENGTH AND TENSILE TESTER AND METHOD The invention relates to methods and means for determining the tensile strength and stretch of sheet material, particularly sheets in the form of woven or nonwoven fabrics and tissue papers.

It is a particular object of the invention to provide a simple, compact device for quickly testing tensile strength and/or stretch of sheet material under varying test conditions.

It is another object of the invention to provide a novel method for reproducibly measuring the tensile strength and/or stretch of lightweight sheet material.

Other objects and advantages will be apparent upon reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is a perspective view of one form of apparatus useful in the practice of the invention;

FIG. 2 is a somewhat enlarged fragmentary view partially in section particularly illustrating the cooperative relationship of the clamping device and penetrative probe of FIG. 1; and

FIG. '3 is a view like that of FIG. 2 but illustrating the clamp device and probe of the test apparatus in operative position.

Referring now to the drawings more in detail, the number (FIG. 1) designates a base having upwardly thereon a pair of vertically extending parallel disposed fixedly positioned support plates 12. Mounted on the top of said supports are horizontally extending fixed guides 14 having notched inwardly facing edges 16. Slidably positioned plates 18 are mounted in cooperative engagement with guides 14 so as to form a surface 20 having an adjustable elongated opening 22 over which a sample may be placed for testing. One of the guides 14 preferably is inscribed with indicia 24 marking the centerline and distance on either side for the purpose of measuring and adjusting the size of opening 22. Set screws 26 provided on guides 14 keep the plates 18 in a desired position, and knobs 28 serve for ease of adjustment. Also supported by base 10 is vertically disposed rearward column 30 which supports mount 32. The mount 32 includes arm 36 extending frontward and having ball bushing bearing 38 for the purpose of slidably mounting vertically disposed guide 40. Mount 32 also includes horizontally disposed support 42 to which guide 40 is attached. Support 42 also engages spring scale 44 by means of set screw 46. Clamp plate 48 is vertically adjustably mounted to support 42 by means of rods 50 and openings 52 including ball bearings 100 in combination with collars 54. Plate 56 is fixedly attached to the top of guide 30 and supports motor 58 as by means of bolts 60 or the like. The motor is connected by cable or wiring indicated generally at 62 to a power source (not shown) and drives eccentric mechanism 64 in rotational movement causing vertical motion of guide 40 and the spring scale 44 as well as clamp plate 48 through rotation of shaft 94 within arm 68 by rack and pinion gearing (not shown). Pivotable guard 96 is included for protection from the gears. Gear rack 66 is connected to eccentric drive 64 by pin 70 through yoke 104 and includes teeth 72 for engagement with the rack and pinion gearing and shaft 94. The spring scale 44 having a gauge 76 is attached to guide 40 at its top by means of clamp 78 and bolt 80 so that it moves vertically therewith. Depending from spring scale 44 by means of shaft 82 is guillotine probe 84 which is positioned in alignment vertically with slot 86 in clamp plate 48 and opening 22 between slide plates 18. Preferably the edge 106 of probe 84 to contact the sample is rounded in cross-section so as not to present a sharp edge that might tear a test sample. For example, a probe one-fourth inch thick would have a Va-inch radius of curvature in cross-section.

For the operation of the device there is provided a switch box 88 having toggle switch 98 which may be so provided with controls as to permit either continuous operation of motor 58 or such as to provide for intermittent, that is, jogging action of the motor and eccentric drive mechanism so that the operator can raise the clamp and probe to insert a sample. Such switches are not shown'in detail as they form no part of the present invention and such equipment is well known to the art.

The opposing edges of slide plates 18 which define opening 22 may include a strip 90 of gripping materials such as xi-inch Kraft adhesive tape or fine grit paper to aid in retention of the sample to be tested.

It is preferred that the device be maintained and operated in a controlled environment such that the temperature is about 73.5F i 35F and the humidity about 50 percent RH. i 2 percent R.H. so that the effect on the test results of these factors will be minimized. To adjust the device for operation, clamp plate 48 is set about one-fourth inch above slide plates 18 at the uppermost clamp plate position. For this purpose collars 54 may be shifted vertically. Slide plates 18 are then adjusted laterally to provide the desired dimensions .of opening 22. For example, when it is desired to test facial tissue tensile strength or multipleply toilet tissue detaching strength, an opening of about l-inch span is preferred. The guillotine probe 84 is then adjusted to a position where the bottom contact edge 106 of the probe is even with the bottom of clamp plate 48. Bracket 78 to spring scale 44 provides for this adjustment in combination with set screws (not shown) on the back of the spring scale.

Preparation of the test samples 92 is done according to the test being performed. For tensile strength tests the samples are preferably cut into 3-inch widths of sufficient length (usually about 8.0-inches) to prevent slippage between clamp plate 48 and slide plates 18. About 5 samples in each direction i.e., machine direction (MD) and cross machine direction (CM) are used for each test. By machine direction is meant the direction parallel to the length of the ordinary paper machine and in which the paper is wound. By cross machine direction is meant the direction orthogonal to the machine direction and parallel to the axis of the wound rolls. These terms are well known to this art and are used in their ordinary sense. When the samples are to be tested for panel detaching, i.e., perforation strength, it is preferred that they be folded lengthwise. For example, the toilet tissue samples are preferably folded once while paper towels are folded in this direction twice.

After the samples have been prepared, the span opening of slide plates 18 is then set as desired, e.g., 1- inch for facial tissue tensile strength. Maximum hold control 45 is set to its neutral position returning the pointer to its initial point, and the dial 47 on spring scale 44 is set to zero by rotating bezel 49. Motor 58 is turned on, and clamp plate 48 is raised to its uppermost position along with spring scale 44 and probe 84. Maximum hold control 45 is set at its lowest position so that the pointer will be held at its highest reading during the next test.

For tensile strength measurements the sample is placed symmetrically under clamp plate 48 on slide plates 18 so that its longer dimension is parallel to the sliding direction of plates 18. The motor is once again started whereby eccentric drive mechanism 64 forces the probe 84 and scale assembly downward through the clamp plate which bears against springs 51 and then returns them to the uppermost position unless the motor is stopped. In this manner the clamp mechanism operates automatically to retain the sample, a feature which is highly advantageous. The test value may be read from dial 47 in units such as grams or pounds. The five samples in each direction are tested and then averaged for a value for each series. The dial is reset to zero between individual tests.

In the case where the detaching strength of single or multi-ply perforated samples such as towelling or toilet tissue is being tested, the procedure is as set forth above except that the sample is perforated and placed over the opening with the perforation aligned directly under and parallel with the length of the guillotine probe.

While it is not desired to limit the invention to any particular theory, it is believed that it measures the tensile energy absorption of the material including that attributable to stretch. In order to make the test results directly comparable with conventional test results obtained with other instruments such as the lnstron tensile tester, it is preferred that a series of duplicate tests be performed with the conventional device and with the tester of this invention at varying dimensions of opening 22. For a given test and material there will be a specific span at which the two tests will be directly comparable.

It is to be noted that the eccentric mechanism specifically described is a preferred embodiment but that many other devices might be employed in the actuation of the probe and clamp plate means. Basically, such a device is required to move the clamp plate and probe into and out of a position in which the clamp plate retains the sample and the probe engages it with means being provided for measurement of the force applied.

The device described and test methods outlined herein have proved thoroughly reliable in extensive tests; however it is contemplated that the invention is not limited to the specific structures and methods shown but it is recognized that various modifications are possible and practical within the scope of the invention claimed.

I claim:

1. Test device for measuring the tensile strength sheet material comprising,

a horizontal support surface adapted to receive a sample of said sheet material and having an elongated opening of a width that is adjustable to provide varying test conditions,

a vertically adjustable clamp plate having an opening in correspondence with the opening in said horizontal su rt, said clam late bein ada ted to engage saiii s imple of she t inaterial 5nd ni aintain it in position over said opening,

a probe adapted to pass through said openings and having an elongated base for contact with said sample,

means for driving the probe downward against said sample and returning it to an upward position out of contact with said sample, and

means for measuring the force applied by said probe against the sample.

2. The test device of claim 1 wherein said horizontal support comprises slidably positioned plates and guides therefor and wherein at least one of said guides is suitably marked with indicia for indicating the dimensions of the opening.

3. The test device of claim 2 wherein said slidably positioned plates have affixed thereto gripping material adapted to aid in retaining a sample.

4. The test device of claim 1 wherein said vertically adjustable clamp plate is spring mounted so as to retain a sample firmly while allowing the probe to pass therethrough and contact the sample.

5. The test device of claim 1 wherein said probe base is rounded in cross-section.

6. A method of testing the tensile strength of sheet material comprising the steps of providing a horizontal support surface having an elongated opening of variable width,

adjusting the width of said opening in accordance with duplicate tests performed on a test device the I results of which it is desired to approximate, positioning a sample of said sheet material over said opening,

maintaining said sample in position by a clamp,

driving a probe having an elongated edge against said sample, and

measuring the force applied by said probe against the sample.

7. The method of claim 6 wherein said sample includes multiple plys of material.

8. The method of claim 6 including the step of perforating said sample and thereafter positioning it over said opening so that the perforation is aligned under said probe. 

1. Test device for measuring the tensile strength of sheet material comprising, a horizontal support surface adapted to receive a sample of said sheet material and having an elongated opening of a width that is adjustable to provide varying test conditions, a vertically adjustable clamp plate having an opening in correspondence with the opening in said horizontal support, said clamp plate being adapted to engage said sample of sheet material and maintain it in position over said opening, a probe adapted to pass through said openings and having an elongated base for contact with said sample, means for driving the probe downward against said sample and returning it to an upward position out of contact with said sample, and means for measuring the force applied by said probe against the sample.
 2. The test device of claim 1 wherein said horizontal support comprises slidably positioned plates and guides therefor and wherein at least one of said guides is suitably marked with indicia for indicating the dimensions of the opening.
 3. The test device of claim 2 wherein said slidably positioned plates have affixed thereto gripping material adapted to aid in retaining a sample.
 4. The test device of claim 1 wherein said vertically adjustable clamp plate is spring mounted so as to retain a sAmple firmly while allowing the probe to pass therethrough and contact the sample.
 5. The test device of claim 1 wherein said probe base is rounded in cross-section.
 6. A method of testing the tensile strength of sheet material comprising the steps of, providing a horizontal support surface having an elongated opening of variable width, adjusting the width of said opening in accordance with duplicate tests performed on a test device the results of which it is desired to approximate, positioning a sample of said sheet material over said opening, maintaining said sample in position by a clamp, driving a probe having an elongated edge against said sample, and measuring the force applied by said probe against the sample.
 7. The method of claim 6 wherein said sample includes multiple plys of material.
 8. The method of claim 6 including the step of perforating said sample and thereafter positioning it over said opening so that the perforation is aligned under said probe. 